Print chain assembly for high speed printer

ABSTRACT

A print chain structure for a high speed printer, wherein an endless dual timing belt has a series of teeth on an inner surface thereof for engagement with a belt driving mechanism. The belt also has a series of teeth on its outer surface. A series of printing elements include interruptions which mechanically and removably cooperate with interstices of the teeth on the outer surface of the belt so that the belt-driving mechanism may efficiently drive the printing elements and the elements may be readily removed for servicing when the need arises. An improved guiding means is also provided for controlling the high speed movement of the printing elements with the belt.

United States Patent 1 Hansen et ,al.

[ Nov. 27, 1973 PRINT CHAIN ASSEMBLY FOR HIGH SPEED PRINTER [75]Inventors: Robert L. Hansen; Clyde C. Roshon,

both of San Jose, Calif.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: June 21, 1971 [21] Appl. No.: 155,003

52 us. or. 101/93 (3, 101/111 51 Int. Cl B41j 5/08 [58] Field of Search10l/93 C, 111, 109,

[56] References Cited UNITED STATES PATENTS 2,222,333 11/1940Wenz/eletal 101/381 2,643,609 6/1953 Gottscho.... l0l/377 2,936,7045/1960 Hense 101/93 C 3,209,682 10/1965 Cooper et al.. 101/109 3,379,1254/1968 Antonucci 101/93 C 3,402,657 9/1968 Potter et al.... 101/111 X3,416,442 12/1968 Brown et al.... 101/93 C 3,577,919 5/1971 Hinze 101/93C 3,621,778 11 1971 Rippleet a]. ..,101/93 c l/l972 Edwards lOl/lll2/1972 Dr eja et al. lOl/93 C OTHER PUBLICATIONS IBM TechnicalDisclosure Bulletin-VoL 13 No. 11 April 1971 Pages 3366-3367.

[57] ABSTRACT A print chain structure for a high speed printer, whereinan endless dual timing belt has a series of teeth on an inner surfacethereof for engagement with a belt driving mechanism. The belt also hasa series of teeth on its outer surface. A series of printing elementsinclude interruptions which mechanically and removably cooperate withinterstices of the teeth on the outer surface of the belt so that thebelt-driving mechanism may efficiently drive the printing elements andthe elements may be readily removed for servicing when the need arises.An improved guiding means is also provided for controlling the highspeed movement of the printing elements with the belt.

5 Claims, 6 Drawing Figures PAIENTEBnnv 2 7 I975 SHEET 1 BF II I] II [III II II II II 1}" II III! ll II III FIG.1

INVENTORS ROBERT L.HAN$EN CLYDE C ROSHQN ATTORNEY PRINT CHAIN ASSEMBLYFOR HIGH SPEED PRINTER BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to a chain printer, and 'moreparticularly to a structure for movably supporting a series of printingelements in high speed chain printers.

2. Description of the Prior Art In chain printers of a type commonlyusedtoday, a chain of uniformly spaced apart print elements or typeslugs is moved at constant speed in a continuous path. A portion of thepath is located on a print line extending transversely of a recordreceiving web, such as a paper. The paper is fed intermittently, line byline, into registry with the print line, by a feed mechanism that iscontrolled either manually or electronically. A plurality of hammerslocated respectively adjacent toprint columns in the print line, areoperated selectively by computer controlled electronic firing circuitsto impress a selected type character of a print element against a ribbonand paper backed by a platen, as that type character moves into registrywith a print column near which the selected hammer is located.

The aforementioned chain of print elements has most commonly involvedthe provision of an endless carrier loop, which comprises either aseries of interconnected links or a unitary flexible belt. The flexiblebelt is considerably less expensive than the interconnected links,

and provides superior service-free performance and long life for manyhigh speed printer applications. For attaching the print elements to theflexible belt, various techniques have been utilized in the prior art.One such technique has been to rivet to the belt a supporting shoe,which serves as a carrier for each'of the type ele ments. Anotherapproach has been to couple each printing element to the flexible beltby means of me-.

ements and an endless flexible belt, which enhances the servicability ofthe printing elements while at the same time affording substantialeconomy in manufacturing and material costs.

SUMMARY OF THE INVENTION An important object of this invention is toprovide an extremely reliable print chain assembly for high speed chainprinters, which includes an endless belt that supports a plurality ofreadily disassemblable type elements.

Another object of this invention is to provide an improved print chainassembly which includes an endless dual timing belt and a plurality ofprinting mechanisms removably and mechanically coupled to the belt.

A further object of the present invention is to provide an improvedprint chain assembly which incorporates a dual timing belt having teethdisposed on its inner and outer surfaces, and a plurality of printingelements drivably and removably cooperable with the teeth on the outersurface of the belt.

In carrying out my invention in one form thereof, it is applied to ahigh speed chain printer which includes a continuous or endless dualtiming belt characterized by a series of accurately spaced teethdisposed on each of its inner and outer surfaces'The teeth on the innersurface of the dual timing belt are engaged by a belt driving means fordriving the belt in a continuous predetermined fashion. A plurality ofprinting elements are disposed on the outer surface of the belt. Theseprinting elements each include a supporting shoe having one or moreoutwardly facing interruptions formed on it. These interruptionscooperate with the teeth on the outer surface of the belt, to providemechanical coupling between the elements and the belt. With such anarrangement, the belt driving means acts upon the inner teeth of thebelt to concurrently drive both the belt and the printing elements, andthe printing elements may be readily removed from mechanical cooperationwith the belt for purposes of servicing. For guiding and controlling themovement of the elements with the belt, each shoe also includes a pairof resiliently operable guiding arms. These arms coact with a guidingshoulder of a printer cartridge to help accurately control the highspeed movement of the printing elements.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects, features andadvantages of this invention will beapparent from the following de- FIG.3 is an enlarged view of a portion of the print chain assembly, to showin greater detail the interrelationships. of the print elements, beltand sprocket wheel;

FIG. 4 is a back view of the printer cartridge of FIG.

I Land FIG. 5 is an alternative embodiment of the printing element. r

FIG. 6 is a partially broken away, three-dimensional view of the printercartridge.

DETAILED DESCRIPTION Referring now to the drawings, there is shown inFIGS. 1, 2 and 3 a front printing chain printer having a type carrier 10which travels in a substantially vertical plane in front of a series ofprint hammers 12. A series of printing elements M are mounted on thetype carrier 10. Each of the printing elements 14 resembles a handhaving four flexibly movable fingers 16 (FIG. 3). The finger 16 has atype slug 17 secured to one of its faces near the free end thereof, toproduce the selected character when each finger 16 is struck by theprint hammer 112. The type slug orcharacter is pressed into engagementwith a ribbon m and a record member 20 (FIG. I) that is backed by asuitable platen member 22.

The hammers l2;have faces which each traverse the I span of a pluralityof adjacent print positions. Control of printing is accomplished by asuitable hold coil 23 which holds all hammers 12 in the retractedinoperative position and individual bucking coils 25 which areselectively actuated to release and cause the associated hammer tocomplete a cycle of operation. The character or printing slug 17 of theprinting finger 16 selected is aligned before an appropriate protrusionon the face of the print hammer 12 so that the appropriate selected typeslug 17 may be printed while the other type slugs 17 are not contactedby the hammer face and are consequently not printed. When the hammer 12strikes the type slug 17 onto the platen member 22, the hammer reboundsand the hold coil flux reattracts the hammer to the inoperative positionso that the hammer is then in a position to be selected for anotherprinting position. The signal to energize the bucking coil is generatedby a suitable control means. This control means provides stored codeddata of the text to be printed for a complete line and this data iscompared with the coded data representing the print element in positionfor printing at each print position. This print element position isestablished by the combination of a home pulse generated by theappropriate hand, and a column by column emitter at the input driveshaft. An equal compare produces a signal which is coupled to actuatethe proper print hammer for printing the designated character at thedesignated print position. A similar operation is conducted at each timedesignated characters on the chain reach a print position, until thecomplete line is printed.

As further shown in FIGS. 1-4 of the drawings, the printer comprises acartridge 24 wherein there is located the type carrier mounted to bedriven by a pair of sprocket wheels 26. The wheels 26 are driven from asuitable drive motor. The cartridge 24 includes a front housing portion28, and a rear housing portion 30, which are suitably fastened togetherto provide a compact type of removable support for the type carrier 10and its printing elements 14. Rear housing portion 30 provides a basefor supporting the type carrier and printing elements 14, and fronthousing portion 28 provides a cover for enclosing the carrier mechanismin the housing. When the front and rear housing portions 28, 30 ofcartridge 24 are fastened together, they provide suitable guidesurfaces, which will be described further hereinafter, that act tocontrol the path of movement of the printing element 14.

To provide an efficient and economical means for driving the printingelements 14 while also enabling them to be readily removable from thecartridge 24, in accordance with the present invention, the type carrierassembly is specially constructed as shown in FIG. 3. Carrier 10 is anendless and flexible belt having on its inner surface a plurality ofuniformly spaced internal teeth 32 between which there are locted aseries of interruptions 34. Teeth 32 mesh with the external teeth ofsprocket wheels 26. In similar manner to the inner surface of carrier10, on its external surface, there is located a series of uniformlyspaced external teeth 36 separated by a series of outwardly facinginterruptions As further shown in FIG. 3, the four flexible fingers 16of each printing element 14 extend upwardly from an integralinterconnecting base portion 40. Also attached to base portion 40 ofelement 14, there is a shoe 42. The shoe 42 is constructed to provide alower section 44, the bottom 44a of which includes a series ofrelatively fiat protrusions 48 uniformly spaced apart and separated fromeach other by interruptions 50. The size and spacing of the protrusions48 and interruptions 50 of lower section 44 of shoe 42, is such that theprofile thereof meshes with the size and'spacing of the external teeth36 and outside interruptions 38 of the type carrier 10. As a result, theshoe 42, which supports each printing element 14, is removablyinterengageable with the external periphery of the type carrier 10, andmay readily drive the printing elements 14 around the wheels 26.

As shown by FIG. 3, the shoe 42 of the printing element 14 has a breadthof generally the same size as the distance between the outer edges ofthe four fingers of element 14. In addition, from viewing FIG. 2, itwill be noted that shoe 42 is considerably thicker than hands 16 andbight section 40. On the rear side of the shoe 42 (i.e. the left side ofFIG. 2) there is a horizontal ledge 51 for supporting the bottom ofbight section 40, and on the front side of shoe 42 (i.e., the right sideof FIG. 4) there is an upwardly facing guiding section 52. The guidingsection 52 includes a pair of outwardly extensive cantilevered arms 54and 56 (FIG. 3). From viewing FIG. 3, it will be noted that one side ofshoe 42 is positioned vertically relative to the type carrier or belt 10by means of the engagement of protrusions 48 and interruptions 50 of theshoe with external teeth 36 and interruptions 38 of the carrier 10. Theother side of the shoe 42 is generally positioned vertically formovement with the belt by means of the resilient engagement of guidingsections 52, and arms 54, 56 with a loopshaped downwardly facingshoulder 60 formed as part of a guiding groove on the rear housingportion 28. (See FIG. 2)

More specifically shown in three-dimensional in FIG. 6, the cartridge 24comprises front and rear housing portions 28, 30, respectively, whichare formed with guide surfaces 62, 64. These surfaces 62, 64 form acontinuous slot slightly wider than the thickness of the printing fingerl6 and guide the fingers as the type element 14 is driven in an endlesspath by the carrier or belt 10. The rear housing portion 28 is formedwith a loop-shaped channel or groove sized to receive the carrier orbelt 10 and the shoe 42 of the printing element 14 engaged therewith.The loop-shaped channel is partially formed by a shoulder 60, whosesurface is in sliding contact with the guiding section 52 of the shoe 42as the print element 14 moves along the channel. At the loop portions ofthe channel, the cantilevered arms 54 and 56 also come into slidingcontact with the shoulder 60.

With carrier 10 being driven around sprocket wheels 26 at a relativelyhigh rate of speed, the resilient cantileveredarms 54 and 56 engagein'cam-like fashion with the facing surface of shoulder 60 so that theflexible fingers 16 are maintained in a direction generallyperpendicular or normal to the direction of movement of the carrier 10.In view of the resilient capability of the arms 54, 56, the printingelements 14 are continuously maintained in a desired position ofvertical alignment relative to the flexible belt while the printer is inoperation.

To provide continuous front to rear (or horizontal) alignment of theprinting elements 14 (viewing FIG. 2) during their movement within thecartridge 24, a guiding surface 62 of cover housing portion 30 andguiding surfaces 64 of the base housing portion 28, are positioned incontiguity with adjacent front and rear faces of base portion 40 of thetype element 14.

To enable any of the printing elements 14 to be readily removed from andreplaced in the cartridge housing without disassembling the cartridgehousing halves 28,

30, an access doorway 70 (FIG. 4) is provided in the rear housingportion 30. Doorway 70 is constructed so that it is disposed oppositethe lower horizontal path of the print elements 14 so that any printelement may be readily removed from the access doorway 70. When theprinter is in normal operation, the doorway 70 is suitably closed by adoor (not shown).

With such an arrangement as that described and shown, an economical dualtiming belt may be conveniently used for the type carrier 10. Such abelt, which is of well known standard construction, is also readilyavailable on the market and is low in cost. In view of the fact that theprinting elements 14 are each driven by means of a profile or matchingtooth type cooperation with external teeth and associated interruptionsin the external periphery of the dual timing belt, the type elements maybe readily removed for convenient servicing through an individual accessdoorway without removing the printer chain from its housing.

The actual print hammer actuator arrangement used may be of anyparticular type. The type hammer actuator shown in FIG. 2 is thatdisclosed in U.S. Pat. No. 3,460,469, entitledPrint Hammer Actuator, andassigned to the same assignee as the present invention. Such a hammeractuator assembly involves a plurality of print actuators 72 mounted ina side-by-side array. Each of the actuators 72 comprises a magnetic corestructure 74 forming a substantially closed path shaped to form twolaterally offset pole pieces 76, 78. The resilient hammer 12 is mountedwith one point 80 fixed relative to the magnetic core structure 74 andanother point 81 coupled to a movable magnetic member 82. The point 81secured to the movable magnetic member is positioned so that thegeneration of a magnetic flux within the magnetic core structure 74attracts the movable member 82 to complete a magnetic circuit andposition the hammer 14 in a ready position. The bucking coils 25 areprovided for selective energization to release the movable magneticmember 82 so that the hammer 12 produces one cycle of movement.

FIG. 5 shows a modification of the present invention wherein theprintingelement and its supporting shoe are integrally constructed, such as forexample, from a plastic material such as Delrin. Here, type element 114includes a plurality of flexible fingers 116 and an integral shoe 142that has a series of protrusions 148 and interruptions 150. The typeslugs 117 may be integral, inserted mechanically, or molded in place.The type element 114 operates in substantially the same fashion as thetype element 14, in cooperation with the dual belt carrier as previouslydescribed.

it will now therefore be seen that we have provided a new and improvedtechnique for expeditiously driving printing elements from a typecarrier or flexible belt. This structure readily lends itself to printerservicing, while also facilitating high speed operation in conjunctionwith a chain printer.

While in accordance with the Patent Statutes, we have described what atpresent are considered to be the preferred embodiments of thisinvention, it will be obvious to those skilled in the art that variouschanges or modifications may be made therein without departin from thepresent invention.

What we claim is:

l. A print chain assembly for high speed chain printers comprising:

a housing,

a pair of sprocket wheels having teeth thereon mounted within saidhousing;

means for rotatably supporting said wheels on spaced parallel axes;

a print chain trained about said wheels;

said print chain including an endless belt having uniformly spacedinternal teeth on the inner surface thereof to mesh with the teeth ofsaid wheels;

said belt also having a series of external teeth on the outer surfacethereof;

and a plurality of printing elements spaced along the outer surface ofsaid belt, each printing element including a base portion which mesheswith at least one of said external teeth of the belt, so that theprinting element engages said belt, thereby enabling said element to bedriven by the belt along the belt path and yet is removable normal tothe belt path;

guiding means disposed within said housing adjacent said belt andessentially parallel to said belt path for maintaining the base portionof each of said printing element in engagement with said belt, and

means included with said housing for permitting access to and removal ofsaid printing elements from the housing.

2. The print chain essentially described in claim 1 wherein eachprinting element of the print chain includes at least one resilientfinger having a type slug affixed to the free end thereof,

and said base portion connected to the other end of said finger,

said portion including a shoe portionhaving a series of teeth structuredto mesh with the teeth of the outer surface of said belt.

3. The printer described in claim 2 wherein the teeth on the shoeportion of the printing element face in a first direction and said typeslug faces in a second direction, said first and second directions beingdisposed in perpendicular relationship.

4. In a high speed printer, a print chain assembly comprising:

a housing;

a belt contained within said housing;

driving means disposed in said housing and engageable with one sideofsaid belt for driving said belt at high speed, the other side of thebelt having a plurality of teeth;

a plurality of printing elements in contact with said belt, each havinga shoe portion with teeth engaging and meshing with the teeth of thebelt such that the printing elements are driven in a direction along thepath of the belt, but are removable normal to the belt path;

loop-shaped guiding means located in said housing and adjacent said beltand essentially parallel to said belt path for maintaining said printingelements in engagement with said belt when said belt is driven by saiddriving means;

a pair of resilient arms associated with each of said printing elementsand coactable with the loop portions of said guiding means formaintaining the printing elements generally normal to the belt duringmovement of the belt through the loop portions; and

means included with said housing for permitting access to and removal ofsaid printing elements from the housing.

5. The printer described in claim 4 wherein said access and removalmeans housing includes a doorway located on one side of the housing infacial alignment with one of said printing elements coupled to saidbelt; said doorway being larger than and facing one of said ment withsaid doorway.

1. A print chain assembly for high speed chain printers comprising: ahousing, a pair of sprocket wheels having teeth thereon mounted withinsaid housing; means for rotatably supporting said wheels on spacedparallel axes; a print chain trained about said wheels; said print chainincluding an endless belt having uniformly spaced internal teeth on theinner surface thereof to mesh with the teeth of said wheels; said beltalso having a series of external teeth on the outer surface thereof; anda plurality of printing elements spaced along the outer surface of saidbelt, each printing element including a base portion which meshes withat least one of said external teeth of the belt, so that the printingelement engages said belt, thereby enabling said element to be driven bythe belt along the belt path and yet is removable normal to the beltpath; guiding means disposed within said housing adjacent said belt andessentially parallel to said belt path for maintaining the base portionof each of said printing element in engagement with said belt, and meansincluded with said housing for permitting access to and removal of saidprinting elements from the housing.
 2. The print chain essentiallydescribed in claim 1 wherein each printing element of the print chainincludes at least one resilient finger having a type slug affixed to thefree end thereof, and said base portion connected to the other end ofsaid finger, said portion including a shoe portion having a seriEs ofteeth structured to mesh with the teeth of the outer surface of saidbelt.
 3. The printer described in claim 2 wherein the teeth on the shoeportion of the printing element face in a first direction and said typeslug faces in a second direction, said first and second directions beingdisposed in perpendicular relationship.
 4. In a high speed printer, aprint chain assembly comprising: a housing; a belt contained within saidhousing; driving means disposed in said housing and engageable with oneside of said belt for driving said belt at high speed, the other side ofthe belt having a plurality of teeth; a plurality of printing elementsin contact with said belt, each having a shoe portion with teethengaging and meshing with the teeth of the belt such that the printingelements are driven in a direction along the path of the belt, but areremovable normal to the belt path; loop-shaped guiding means located insaid housing and adjacent said belt and essentially parallel to saidbelt path for maintaining said printing elements in engagement with saidbelt when said belt is driven by said driving means; a pair of resilientarms associated with each of said printing elements and coactable withthe loop portions of said guiding means for maintaining the printingelements generally normal to the belt during movement of the beltthrough the loop portions; and means included with said housing forpermitting access to and removal of said printing elements from thehousing.
 5. The printer described in claim 4 wherein said access andremoval means housing includes a doorway located on one side of thehousing in facial alignment with one of said printing elements coupledto said belt; said doorway being larger than and facing one of saidprinting elements when the latter is in alignment with said doorway, tofacilitate the ready removal and replacement of the printing element inalignment with said doorway.